In the conventional crawler-type vehicles, the undercarriage and the track chain, are subject to substantial wear as a result of the severe operating environment. Such wear, in turn causes slack to occur in the track chains. To accommodate the wear and resultant slack, idler wheels are utilized which are periodically adjusted to take up the slack and properly tension the track. Failure to take up the slack not only causes accelerated track wear, but may also cause loss of the track chains as for example, during the turning of the vehicle.
While a number of manually operated track adjusting apparatus have been developed, these have not proven completely successful. Access for manual adjustment is often hindered by the adverse environmental conditions such as the coating of the undercarriage with layers of mud or ice. One type of manually operated adjusting apparatus is disclosed in U.S. Pat. No. 3,013,843, issued Dec. 19, 1961 to Sinko. In this type of adjustment apparatus the idler is rotatably held by a support having at one end a piston, the support being held by a stationary housing having a cylinder to accept the piston. Grease is forced through a fitting into the piston and cylinder interstice resulting in adjustment of the idler with respect to its stationary support.
Another problem in the use of track chain systems is the occasional excessive tension incurred by the track chain as when foreign matter, such as rocks and the like, are drawn between the rack and the elements supporting it. The forces generated by the excessive track tension tends to damage the chain or elements of the system supporting the track chain particularly those elements associated with the idler. Along these lines still another problem encountered is the substantial forces generated by the track chain against the front idlers when the vehicle is being operated in reverse.
Accordingly, various types of recoil apparatus have been developed the most common of those being the use of large, expensive recoil springs. A departure from the simple use of a recoiling spring is found in U.S. Pat. No. 3,901,563, issued Aug. 26, 1975 to Day. Apparatus of this type and the like provide for the idler to be hydraulically adjusted to properly tension the track and enable the idler, by porting of the hydraulic fluid, to recoil. However, the required elaborate porting of the fluid and the use of a horsepower consuming hydraulic motor detract from its commercial utility.
The present invention is directed to overcoming one or more of the above problems set forth above.